macboy said:
Quite an interesting and original topology. Yes we need more of that on this forum.
On the other hand implementing something so simple as the snubbers with such a great positive effect on the overall sound (using bigger PS caps) deserves getting exited about. I think the goal should be a good quality reproduction and as far as I'm concerned, the simple the topology the better. One thing I don't want to see is unnecessary stuff thrown in an amp just to make the circuit look sophisticated (this is not the case with the amp discussed in this thread).
Bottom line, if a resistor placed in a right place improves the performance of the amp as much as adding a preamp, then I'm exited about the implementation of the resistor more than by the implementation of the preamp.
Good work Mauro! And your English is fine too. Keep on talking!
Greg
maupenas said:Hi Andypairo,
The LM318 choice it's extremely determinant (for my). I have tested various OP-amp (NE5534, OP27, TL081, TL071 ecc...), but the audio performance (compareted a class A amplifier) are superior.
An other motivation is that the slew-rate of this OPAMP is suited to this application (or all final amplifier device )
Ok. Did you try the well regarded OPA627 and similar from BB?
I understand Italian quite well
I can help yopu with the translation if you want but I think that you are clear enough.
I've done too much programming lately... must give a look at my electronics books...
So another project on queue....
Where do you live? I'd like to hear the baby singin'
Cheers
Andrea
Good! See.... italians just do it better...
(in Gainclones at least)
If my beliefs are confirmed, this is gonna be the most advanced and good sounding LM3886 implementation. Let's hope it sounds well... and it's not so dependant on expensive op amps!
Ciao a tutti e buona fortuna... Continuate così!
(in Gainclones at least)
If my beliefs are confirmed, this is gonna be the most advanced and good sounding LM3886 implementation. Let's hope it sounds well... and it's not so dependant on expensive op amps!
Ciao a tutti e buona fortuna... Continuate così!
I believe that will like you so as it is. Nothing forbids to try other solutions, but my suggestion is to do it if dispose of suitable tools.
I not have tested OPA627.
I have led by departs JLH 69 and other "clones" for this, but the tastes are taste.
The theoretical treatment do it only if like you the result.
Ciao
Mauro Penasa
I not have tested OPA627.
I have led by departs JLH 69 and other "clones" for this, but the tastes are taste.
The theoretical treatment do it only if like you the result.
Ciao
Mauro Penasa
The Voltage +VRL it's about +24V.
At start up C12 it' s discharge and determined (with R14 charge current) the ON-time delay. At VB Q1 >1,2V the darlington (Q1&Q2) close the Output relay.
If at Ampli out it's present a positive tension with time- costant > several mS (integrated on C19-R42 or R41) and Voltage > 2V (about),
Q3 discharge C12 and Relay are Open. If the status return at 0VDC, C12 are recharge with delay.
If a negative tension are present at ampli out, C12 it's discarge (from R44 or R43 and Q1 base potential are about 0V (or some negative mV) so, Relay it's off.
The Low value of C13 disable immediately the relay on power off state.
Ciao
Mauro
At start up C12 it' s discharge and determined (with R14 charge current) the ON-time delay. At VB Q1 >1,2V the darlington (Q1&Q2) close the Output relay.
If at Ampli out it's present a positive tension with time- costant > several mS (integrated on C19-R42 or R41) and Voltage > 2V (about),
Q3 discharge C12 and Relay are Open. If the status return at 0VDC, C12 are recharge with delay.
If a negative tension are present at ampli out, C12 it's discarge (from R44 or R43 and Q1 base potential are about 0V (or some negative mV) so, Relay it's off.
The Low value of C13 disable immediately the relay on power off state.
Ciao
Mauro
Hi, Greg
Your observation is near, but...
My description is a lot of fast, and non exact (sorry). With the components used in the circuit the threshold of intervention is +5,5VDC @ 0 , 5 sec. and -5, 5V @ 2 sec. The motive is that C12 discharge of 0,3V to stop the relay. Naturally modifying R44 R43 R42 R43 gets the constant and the threshold that is prefered.
Affair remembers that the speed of various intervention to the increase of the tension, and if an ending is spoiled usually in exit there are about tens of volt. In this conditions the intervention becomes < 0,5 sec. even on the negative thing.
Obviously this circuit not doesn't want be an absolute reference, and it is in my scheme because much compacts ( all the circuit is on a 100160mm card ). In the use daily paper has not given never problems and the breakdowns of the prototypes have not damaged never my loudspeakers.
Ciao
Mauro
Your observation is near, but...
My description is a lot of fast, and non exact (sorry). With the components used in the circuit the threshold of intervention is +5,5VDC @ 0 , 5 sec. and -5, 5V @ 2 sec. The motive is that C12 discharge of 0,3V to stop the relay. Naturally modifying R44 R43 R42 R43 gets the constant and the threshold that is prefered.
Affair remembers that the speed of various intervention to the increase of the tension, and if an ending is spoiled usually in exit there are about tens of volt. In this conditions the intervention becomes < 0,5 sec. even on the negative thing.
Obviously this circuit not doesn't want be an absolute reference, and it is in my scheme because much compacts ( all the circuit is on a 100160mm card ). In the use daily paper has not given never problems and the breakdowns of the prototypes have not damaged never my loudspeakers.
Ciao
Mauro
Mauro,
I'm highly intrigued by your design, and would like to understand a bit better.
All designs are a kind of compromise. So there are strong / weak points in all. While I was thinking of it, some weak points came to my mind. If you don't mind, I would list them, so you can tell the reasons behind your tradeoffs.
You are right when saying that the feedback loop impedance characteristics are important for an opamp design. This is where the original Gaincard concentrates, also. It is using low impedance & very short feedback loop. It's impedance seen by the -pin is ~ 600 ohm. The +pin, in an optimal case, when driven by an external pre, or a Cd output, is supposed to see a dynamic impedance of a couple of hundreds ohm, also. So I would say, it is quite balanced for both the inputs. The low impedance input & feedback network is decreasing the input capacitance effects, the input bias current effects. It is decreasing the feedback loop phase shifts to a possible minimum.
The common mode signal showing up at the input is ~30 dB below the output signal level, which is not a small advantage.
In your design the impedance seen by the input pins is precisely equal, 5 kohm for each input. But ~ 8 times higher, than in case of the Gaincard. So the input capacitance & bias current & phase shifts are worse ~ 8 times.
The Common mode signal present at the inputs is half of the output signal! that's 24 dB worse than the Gaincard case!
What I wanted to say with this is that the LM3886 has to work harder in your setup. So it distorts more than in a gaincard case, though this will be compensated for by the extra open loop gain added by the lm318.
The LM 318 is a fast opamp, but then for stability, you have to slow it down, quite heavily. [A side note: you say it's important to have a high slew rate opamp here, though it's output swing is strongly limited, only a few tens of millivolts - though I understand what you want to say here - an opamp's slew rate is determined by it's INPUT circuitry, and we need a fast diff. amp. Hm, I see, though the output voltage is low, the output current for the LM318 is not so low - and its output impedance is open loop for low frequencies ]
So I suppose that the overall speed of the full circuit is lower than that of the Gaincard alone, again.
What you gained in the process is that the open loop overall gain is much higher, so after global feedback you have less distortion;
The output current is buffered from the input diff. amplifier which provides the error signal;
It is possible to use an input opamp with very good input characteristics.
The final product is a high feedback, low distortion, low output impedance voltage amplifier with ~ 30 dB gain.
It seems to me that this is quite against the tendencies presently followed - which is giving up some gain thus lowering the feedback & extending the open loop gain bandwidth, as much as possible.
What I don't see is how this internally applied current buffer would help more, then a common unity gain buffer, or a buffer with some gain?
Ciao, George
I'm highly intrigued by your design, and would like to understand a bit better.
All designs are a kind of compromise. So there are strong / weak points in all. While I was thinking of it, some weak points came to my mind. If you don't mind, I would list them, so you can tell the reasons behind your tradeoffs.
You are right when saying that the feedback loop impedance characteristics are important for an opamp design. This is where the original Gaincard concentrates, also. It is using low impedance & very short feedback loop. It's impedance seen by the -pin is ~ 600 ohm. The +pin, in an optimal case, when driven by an external pre, or a Cd output, is supposed to see a dynamic impedance of a couple of hundreds ohm, also. So I would say, it is quite balanced for both the inputs. The low impedance input & feedback network is decreasing the input capacitance effects, the input bias current effects. It is decreasing the feedback loop phase shifts to a possible minimum.
The common mode signal showing up at the input is ~30 dB below the output signal level, which is not a small advantage.
In your design the impedance seen by the input pins is precisely equal, 5 kohm for each input. But ~ 8 times higher, than in case of the Gaincard. So the input capacitance & bias current & phase shifts are worse ~ 8 times.
The Common mode signal present at the inputs is half of the output signal! that's 24 dB worse than the Gaincard case!
What I wanted to say with this is that the LM3886 has to work harder in your setup. So it distorts more than in a gaincard case, though this will be compensated for by the extra open loop gain added by the lm318.
The LM 318 is a fast opamp, but then for stability, you have to slow it down, quite heavily. [A side note: you say it's important to have a high slew rate opamp here, though it's output swing is strongly limited, only a few tens of millivolts - though I understand what you want to say here - an opamp's slew rate is determined by it's INPUT circuitry, and we need a fast diff. amp. Hm, I see, though the output voltage is low, the output current for the LM318 is not so low - and its output impedance is open loop for low frequencies ]
So I suppose that the overall speed of the full circuit is lower than that of the Gaincard alone, again.
What you gained in the process is that the open loop overall gain is much higher, so after global feedback you have less distortion;
The output current is buffered from the input diff. amplifier which provides the error signal;
It is possible to use an input opamp with very good input characteristics.
The final product is a high feedback, low distortion, low output impedance voltage amplifier with ~ 30 dB gain.
It seems to me that this is quite against the tendencies presently followed - which is giving up some gain thus lowering the feedback & extending the open loop gain bandwidth, as much as possible.
What I don't see is how this internally applied current buffer would help more, then a common unity gain buffer, or a buffer with some gain?
Ciao, George
Hi,Joseph K
your questions are complex, but not don't want give too complex answers.
Gather the things.
Thing is this circuit:
LM3886 is a power bridge Voltage/current.
The fact that with the acquisition values has a behaviour similar to a "Voltage Gain Amplifier"
not change the dynamics of operation, that is different.
the parameters of project are:
Iout = ( R55*Vin)/( R5*R3) ( Vin is the U1 exit ).*
Rout= R3*(R6/%error) ( R6=R55=R5=R8 and %error = tolerance value among the res.)*
With the values of the circuit, and R6 R55 R5 R8 = 1 % matching,the impedance of exit of the bridge is about 1 ohms
and it develops 100 A/V ( then the pilotage is little ).
LM318 it's the drive to the bridge and checks the differential tensions.
This circuit it may consider a variation of " dumping current " ( current power & control voltage ).
to the test, this topology is a lot of effective to check the crossover distorsions that increase when decreasing load )
across the global neg. feedback ( and sound it's good ).
The motive for which have chosen a double invert. is in the greater stability of the 2 OPamp
in this configuration, primarily on account of the exploitation of the input capacity.
LM318: Excellent integrator/comparator ( see the datasheets ). probably the better thing, to this price,
if it comes used with this technique of the signal on the " ground virtual " (-IN).
Other choices: Theoretically ( and practically ) are able use other OPamp to low noise and better DC chars.
To depart the final audio evaluation ( I love LM318 "valve" sound ),
has to consider a suitable high frequency gain margin, and phase, to maintain
stable all. This circuit is the result of a serious long of experiments, among the like some on
techniques of feedforward one's own about to this OPamp (not used).
Then there is the fact that the 100A/V value has been definite only after different technical tests and of listening.
Initially ( and even you praies if want try, is enough lead till 0,1ohm on R3) this value are very smaller.
Besides there is the fact that the loss of profit of IC1 high frequency does works hard of more U1.
Close gain loop, ecc feedback...: closing the ring all is born...
Personally I am not afflicted by paranoias on the negative feedback. How to all the things it can be good or bad. in my case this is rather tall, but
the particular configuration me allows to use it to reduce the distorsion without altering the acustics performances
that to like me, and the margin of drive of U1 helps me to me defend from IMD problem.
Conclusions: a 50W/8ohm Amply, 0,002% THD medium all band (the FFT show traces of the distorsion of the generator, that to 10Khz is 0,0040 %), sound good.
Ciao
Mauro
*National Semi. Applications
your questions are complex, but not don't want give too complex answers.
Gather the things.
Thing is this circuit:
LM3886 is a power bridge Voltage/current.
The fact that with the acquisition values has a behaviour similar to a "Voltage Gain Amplifier"
not change the dynamics of operation, that is different.
the parameters of project are:
Iout = ( R55*Vin)/( R5*R3) ( Vin is the U1 exit ).*
Rout= R3*(R6/%error) ( R6=R55=R5=R8 and %error = tolerance value among the res.)*
With the values of the circuit, and R6 R55 R5 R8 = 1 % matching,the impedance of exit of the bridge is about 1 ohms
and it develops 100 A/V ( then the pilotage is little ).
LM318 it's the drive to the bridge and checks the differential tensions.
This circuit it may consider a variation of " dumping current " ( current power & control voltage ).
to the test, this topology is a lot of effective to check the crossover distorsions that increase when decreasing load )
across the global neg. feedback ( and sound it's good ).
The motive for which have chosen a double invert. is in the greater stability of the 2 OPamp
in this configuration, primarily on account of the exploitation of the input capacity.
LM318: Excellent integrator/comparator ( see the datasheets ). probably the better thing, to this price,
if it comes used with this technique of the signal on the " ground virtual " (-IN).
Other choices: Theoretically ( and practically ) are able use other OPamp to low noise and better DC chars.
To depart the final audio evaluation ( I love LM318 "valve" sound ),
has to consider a suitable high frequency gain margin, and phase, to maintain
stable all. This circuit is the result of a serious long of experiments, among the like some on
techniques of feedforward one's own about to this OPamp (not used).
Then there is the fact that the 100A/V value has been definite only after different technical tests and of listening.
Initially ( and even you praies if want try, is enough lead till 0,1ohm on R3) this value are very smaller.
Besides there is the fact that the loss of profit of IC1 high frequency does works hard of more U1.
Close gain loop, ecc feedback...: closing the ring all is born...
Personally I am not afflicted by paranoias on the negative feedback. How to all the things it can be good or bad. in my case this is rather tall, but
the particular configuration me allows to use it to reduce the distorsion without altering the acustics performances
that to like me, and the margin of drive of U1 helps me to me defend from IMD problem.
Conclusions: a 50W/8ohm Amply, 0,002% THD medium all band (the FFT show traces of the distorsion of the generator, that to 10Khz is 0,0040 %), sound good.
Ciao
Mauro
*National Semi. Applications
Dear Mauro!
please don't misunderstand me - I am aware of the functionality of this config - I would quote myself:
What I wanted to point out, is that there are factors in it's operation which will make it distort, deviate from the ideal transconductance function. [to add to the previously mentioned, there is also the output impedance of the U1, non zero, and which "sees" a load current proportional to the output signal] Then this distortion is corrected by U1.
And it should be emphasised, that your design is visibly very well thought over, refined into the little particulars [like the bypass conf. for IC1; like, indeed, the input compensation / filter cap on U1]
So, really, I am far from attacking You - I was just provoking You, so while in defense, you would make it more clear your design decisions.
Also, I am not questioning the your choice for U1. And anyway, people can [and will..] roll their own.. Some other choices adequate in this position may be the LM6171; AD825; AD8065; AD8033..
May I notice one thing? As far as I understood, the "current dumping" method is useful in eliminating the low signal crossover distortions because of the contribution [included in the bridge] of a second, low power & class A output stage. Here that is missing.
Ciao, George
please don't misunderstand me - I am aware of the functionality of this config - I would quote myself:
What I wanted to point out, is that there are factors in it's operation which will make it distort, deviate from the ideal transconductance function. [to add to the previously mentioned, there is also the output impedance of the U1, non zero, and which "sees" a load current proportional to the output signal] Then this distortion is corrected by U1.
And it should be emphasised, that your design is visibly very well thought over, refined into the little particulars [like the bypass conf. for IC1; like, indeed, the input compensation / filter cap on U1]
So, really, I am far from attacking You - I was just provoking You, so while in defense, you would make it more clear your design decisions.
Also, I am not questioning the your choice for U1. And anyway, people can [and will..] roll their own..
Some other choices adequate in this position may be the LM6171; AD825; AD8065; AD8033..May I notice one thing? As far as I understood, the "current dumping" method is useful in eliminating the low signal crossover distortions because of the contribution [included in the bridge] of a second, low power & class A output stage. Here that is missing.
Ciao, George
From your analysis on the circuit had not doubts.
My answer has been ample to grant even the request for other interlocutors.
The "ideal funtion transconductances" is "distorted" simply because that circuit is a compromise (as all the circuit).
For the precision, U1 introduces an impedance of exit ( open loop ) about to 50 ohms, does that maintains the balancing of the bridge within 1 %.
A perfectionist would be able insert a trimmer in series to R8 to compensate even this problem
(and uses resistances after 0, 1% or select).
the obvious solution to improve is: increasing the value of the resistor. But there is a problem.
Increase the delay of group of IC1 and the bridge shows traces un parasitic capacitance ( C31 eras been scheduled for this problems ).
Sincerely, given that my principal objective is "musical", after has tried practically all the variations,
I have stopped me on a compromise practise. I am sure that some is able find better "balancings".
(I have published this scheme one's own for this!).
U1 matter: I don't want do an extreme defence of LM318, but I have a pragmatic mentality ( the mile resulted to the minor costs ).
To leave the free field, I say at once that probably some of the OPamp that you have quoted better results in my circuit.
I rest "cools" to the "enthusiasms" on the chips because am convinced that the strength of the complex circuits is in their "equilibrium".
Is banal to show that a OPamp of new generation are able improve the things. Naturally, you am happy if succeed to improve the performanceses of this circuit.
Variation of " Current dumping"; This circuit is not "homologated" in accordance with the characteristics of the patent "dumping current"
(what is described as you have said).
I have defined it a "variation" for this, but am open me badly.
The good performances on the crossover THD is that verify on my circuit.
Evidently this circuit gets was characteristic of the " dumping current ", without use entirely his princes.
Is not a lot of difficult to shape this 2 OPamp in stasis, dumping current, feedback current, negative impedences, and with a modest work even something of more amusing, as Power feedforward. In practice, much of this topology is more elaborate of my circuit and don't great improve the performances.
Ciao
Mauro
My answer has been ample to grant even the request for other interlocutors.
The "ideal funtion transconductances" is "distorted" simply because that circuit is a compromise (as all the circuit).
For the precision, U1 introduces an impedance of exit ( open loop ) about to 50 ohms, does that maintains the balancing of the bridge within 1 %.
A perfectionist would be able insert a trimmer in series to R8 to compensate even this problem
(and uses resistances after 0, 1% or select).
the obvious solution to improve is: increasing the value of the resistor. But there is a problem.
Increase the delay of group of IC1 and the bridge shows traces un parasitic capacitance ( C31 eras been scheduled for this problems ).
Sincerely, given that my principal objective is "musical", after has tried practically all the variations,
I have stopped me on a compromise practise. I am sure that some is able find better "balancings".
(I have published this scheme one's own for this!).
U1 matter: I don't want do an extreme defence of LM318, but I have a pragmatic mentality ( the mile resulted to the minor costs ).
To leave the free field, I say at once that probably some of the OPamp that you have quoted better results in my circuit.
I rest "cools" to the "enthusiasms" on the chips because am convinced that the strength of the complex circuits is in their "equilibrium".
Is banal to show that a OPamp of new generation are able improve the things. Naturally, you am happy if succeed to improve the performanceses of this circuit.
Variation of " Current dumping"; This circuit is not "homologated" in accordance with the characteristics of the patent "dumping current"
(what is described as you have said).
I have defined it a "variation" for this, but am open me badly.
The good performances on the crossover THD is that verify on my circuit.
Evidently this circuit gets was characteristic of the " dumping current ", without use entirely his princes.
Is not a lot of difficult to shape this 2 OPamp in stasis, dumping current, feedback current, negative impedences, and with a modest work even something of more amusing, as Power feedforward. In practice, much of this topology is more elaborate of my circuit and don't great improve the performances.
Ciao
Mauro
Joseph K said:
Hello George,
I like your analysis of this highly sophisticated circuit. What intriques me is the refernece to the "bridge" nature, meaning IIUC a current dumping aproach. But I see at the LM3886 a combination of pos and neg feedback, which brings memories of a Howland Current Pump, which is also a type of balanced bridge, to get a VCCS as you or somene else remarked.
In all these cases, the stability issue is very complex and depends on several zeros and poles in the circuit. The many compensation parts also point to this.
It may well be that the LM318 is one of the few that works in this particular circuit. It has a particular OL charateristic and for example has assymetrical slewrates, IIRC, which may also play a role here. IMHO, you cannot just replace opamps at will here like in a buffered gainclone. Here, the open loop opamp characteristic is an integral part of the circuit.
You are right that it goes against the trend by SOME to lower OL gain and wider OL bandtwidth, but as you know that in itself is a controversial issue and by no means universally accepted. For me, there are many ways to skin a cat and this circuit is an interesting one.
Jan Didden
PS I still have a few tighter spec'd LM218's, metal can, if anyone is interested.
Good point of view and good description of the LM318 characteristics,janneman.
Is for this that have chosen this component. The stability of the circuit allows however to use some other type of chips. For what concerns the select philosophy, as I have already said this is the compromise that gave me improve general results, but on this circuit I have experimented nearly all the audio technical known ( driver current , dumping current ,stasis ecc...). The choice to working with all the negative feedback in this circuit has been taking simply because things rang better ( I have tried even to replace U1 with differential discrete circuits, with greater band and low OL gain, but without substantial improvement). Perhaps an excellent audio result would be able get using the current bridge in stasis configuration with a valve voltage driver, or high quality discrete solutions.
Mauro
Is for this that have chosen this component. The stability of the circuit allows however to use some other type of chips. For what concerns the select philosophy, as I have already said this is the compromise that gave me improve general results, but on this circuit I have experimented nearly all the audio technical known ( driver current , dumping current ,stasis ecc...). The choice to working with all the negative feedback in this circuit has been taking simply because things rang better ( I have tried even to replace U1 with differential discrete circuits, with greater band and low OL gain, but without substantial improvement). Perhaps an excellent audio result would be able get using the current bridge in stasis configuration with a valve voltage driver, or high quality discrete solutions.
Mauro
Dear Jan!
First of all, would like to emphasise again that also I 'am really happy that You are back! [and as sharp as ever].
Yes, this sophisticated circuit by Mauro IS a Howland Current Pump application, and his reference to a bridge was exactly in the way that you described.
And it is really interesting, and also his another, new thread. The best thing would be to be able to listen to his creations, it's a pity that, as far as I understood, we are not exactly neighbours.
In my "analysis" I was just thinking aloud about his possible reasons behind his choice of this more complicated circuit, instead of the simple basic application. As far as I understood, his point is an improvement on the input section of the LM3886. And it can be a valid point.
Also I wanted to show that it is a different approach, with respect to the "Gaincard" thinking, which emphasizes on the speed of the feedback loop.
And it is not that simple to substitute that opamp, I agree. This design of his is really a very well thought over, blanced one. I tried to list some opamps, which are known for good sound, and are having similar characteristics to the LM318.
What were You having in mind with the assymetrical slew rates? It is time to learn for me!
And If Mauro would be so kind to explain more extensively his point about the output Zobel causing stability problems, it would be very interesting, as well.
Ciao, George
First of all, would like to emphasise again that also I 'am really happy that You are back! [and as sharp as ever].
Yes, this sophisticated circuit by Mauro IS a Howland Current Pump application, and his reference to a bridge was exactly in the way that you described.
And it is really interesting, and also his another, new thread. The best thing would be to be able to listen to his creations, it's a pity that, as far as I understood, we are not exactly neighbours.
In my "analysis" I was just thinking aloud about his possible reasons behind his choice of this more complicated circuit, instead of the simple basic application. As far as I understood, his point is an improvement on the input section of the LM3886. And it can be a valid point.
Also I wanted to show that it is a different approach, with respect to the "Gaincard" thinking, which emphasizes on the speed of the feedback loop.
And it is not that simple to substitute that opamp, I agree. This design of his is really a very well thought over, blanced one. I tried to list some opamps, which are known for good sound, and are having similar characteristics to the LM318.
What were You having in mind with the assymetrical slew rates? It is time to learn for me!
And If Mauro would be so kind to explain more extensively his point about the output Zobel causing stability problems, it would be very interesting, as well.
Ciao, George
Joseph K said:
George,
What I wanted to say is that this circuit is really an integrated circuit in the real sense. In a buffered gain clone, you can play around all you like with the buffer from an engineering pov. In this case, changing the LM318 to something else will almost surely require other changes for stability. The assymmetrical slewrate (which we don't see anymore with more recent opamps) may be important in this circuit, that is all I wanted to say. Otherwise I fully agree with you.
Jan Didden
Hi Mauro,
Does your circuit will work with other type of chip amp such as TDA 7294 ? I have some of them doing nothing so I wonder if it will works with your circuit.
The same question I will ask to you for your Stasis circuit.
LM 3886 and LM 3875 is not easy to find around here, but plenty of TDA 7294.
Thanks,
Gede
Does your circuit will work with other type of chip amp such as TDA 7294 ? I have some of them doing nothing so I wonder if it will works with your circuit.
The same question I will ask to you for your Stasis circuit.
LM 3886 and LM 3875 is not easy to find around here, but plenty of TDA 7294.
Thanks,
Gede
I excuse me for the delay of the answer.
I have not make a will this chips, but if they have a similar open loop gain and phase margin are able use them. Eventually you have to retouch the R8 C1 net in the "stasis" version if see of the instabilities ( free or induced oscillations by the load ).
If it's of interest, am working to an (radical) improved version of this circuit, on the basis of the "stimuluses" of Jan and Joseph. the results are: improving of the THD and of the quality of the sound. If it is of interest to some, provided that me signal it
Ciao
Mauro
I have not make a will this chips, but if they have a similar open loop gain and phase margin are able use them. Eventually you have to retouch the R8 C1 net in the "stasis" version if see of the instabilities ( free or induced oscillations by the load ).
If it's of interest, am working to an (radical) improved version of this circuit, on the basis of the "stimuluses" of Jan and Joseph. the results are: improving of the THD and of the quality of the sound. If it is of interest to some, provided that me signal it
Ciao
Mauro